I'd recommend Dundjinni + CSUAC art pack (CSUAC Downloads). That should let you build a large map which you can export at your desired resolution. Note that the resolution of the exported map is limited by the individual resolution of the tiles you've used in constructing the map. Even if you don't use Dundjinni the CSUAC art pack contains a lot of useful textures. Part of the experience of being a cartographer is collecting a useful set of textures for the kinds of maps you want to make.